Endometriosis is a chronic disease characterized by the growth of the endometrium outside the uterine cavity. In response to estradiol, this tissue begins to proliferate and grow, forming lesions and nodules, which can invade the tissues, causing pelvic pain and infertility. The most widely used pharmacological treatment is progesterone, which manages to reduce symptoms, but approximately one-third of patients develop resistance to treatment. Aim: To determine the expression levels of progesterone receptors in biopsies of recto-vaginal nodules, considering central and invasive regions of the lesions. Materials and methods: Biopsies from 16 patients diagnosed with deep endometriosis were used, and fragments from the center of the nodule and the invasive area were selected. Histological sections and immunohistochemical staining for progesterone receptors, KI67 and E-Cadherin (ECad) were prepared and quantified by image analysis. Results: The glands in the center (less invasive area) compared to the front (invasive area) have a significantly lower level of mitosis (KI67 0,486 +/- 0,014 vs. 0,719 +/- 0,026 +nuclei/total nuclei) and greater thickness (13,430 +/- 0,169 vs. 6,160 +/- 0,166 mu m), higher level of ECad expression (0,525 +/- 0,048 vs. 0,338 +/- 0,063 times over control), and higher expression of RP (stroma 0,382 +/- 0,267 vs. 0,165 +/- 0,191 and epithelium 0,728 +/- 0,043 and 0,386 +/- 0,063 times over control). Conclusion: The glands have different molecular and morphological characteristics depending on the area of the lesion. Invasive areas are more proliferative and express fewer progesterone receptors. However, further studies are required to determine if these differences translate into the ability to respond to progesterone treatment.